Optical system having stable resonator

Abstract

In an optical system having at least one optical part other than mirrors, for example, a wavelength conversion optical system which uses an external resonator, an optical system which is capable of solving the problem of transverse mode generation due to the existence of scattering matter and the optical crystal used and capable of supplying a stable output (stable wavelength conversion output) is provided. At least at one point in a stable resonator having optical parts (optical crystal) other than mirrors, an aperture having a circular hole with a diameter 1 to 10 times the diameter of a beam at the aperture, a slit having a width 1 to 10 times the diameter of the beam, or an aperture of an arbitrary shape having an edge is located, or a knife edge having an linear or curved edge is Located so that the nearest distance between the edge and the beam is 1 to 10 times the radius of the beam from the center of the beam.

What is claimed is:  
     
       1. An optical system having a resonator which is an optical system having at least one optical part other than mirrors in a stable resonator provided with, on at least one point in said stable resonator, an aperture having a circular hole with a diameter of 1 to 10 times the beam diameter at each point, said resonator further comprising a non-linear optical crystal including a borate material, wherein said optical system generates ultraviolet rays. 
     
     
       2. An optical system having a resonator as claimed in claim  1 , wherein said optical system is a wavelength conversion optical system having at least one optical part other than mirrors in an external stable resonator, and said optical system is provided with, on at least one point in said external stable resonator, an aperture having a circular hole with a diameter of 1 to 10 times the beam diameter at each point. 
     
     
       3. An optical system having a resonator which is an optical system having at least one optical part other than mirrors in a stable resonator provided with, on at least one point in said stable resonator, a slit having a width 1 to 10 times the beam diameter at each point, said resonator further comprising a non-linear optical crystal including a borate material, wherein said optical system generates ultraviolet rays. 
     
     
       4. An optical system having a resonator as claimed in claim  3 , wherein said optical system is a wavelength conversion optical system having at least one optical part other than mirrors in an external stable resonator, and said optical system is provided with, on at least one point in said external stable resonator, a slit having a width 1 to 10 times the beam diameter at each point. 
     
     
       5. An optical system having a resonator which is an optical system having at least one optical part other than mirrors in a stable resonator provided with, on at least one point in said stable resonator, a slit having a width 1 to 10 times the beam diameter at each point, wherein said optical system is an optical system having at least one optical part other than mirrors in a stable resonator, and said optical system is provided with, on at least one point in said stable resonator, at least two slits having a width 1 to 10 times the beam diameter at each point which intersect each other at a certain angle. 
     
     
       6. An optical system having a resonator which is an optical system having at least one optical part other than mirrors in a stable resonator provided with, on at least one point in said stable resonator, a slit having a width 1 to 10 times the beam diameter at each point, wherein said optical system is a wavelength conversion optical system having at least one optical part other than mirrors in an external stable resonator, and said optical system is provided with, on at least one point in said external stable resonator, at least two slits having a width 1 to 10 times the beam diameter at each point which intersect each other at a certain angle. 
     
     
       7. An optical system having a resonator which is a wavelength conversion optical system having a plurality of mirrors and a non-linear optical crystal including a borate material for functioning as a wavelength conversion element in a resonator provided with, on an arbitrary space in said resonator comprising said plurality of mirrors and optical crystal, an aperture having an edge of arbitrary shape, wherein said system generates ultraviolet rays. 
     
     
       8. An optical system having a resonator as claimed in claim  7 , wherein said optical system is a wavelength conversion optical system having a plurality of mirrors and an optical crystal for functioning as a wavelength conversion element in an external stable resonator, and said optical system is provided with, in an arbitrary space in said external stable resonator comprising said plurality of mirrors and optical crystal, an aperture having an edge of arbitrary shape. 
     
     
       9. An optical system having a resonator having at least one optical part other than mirrors in a stable resonator provided with, on at least one point in said stable resonator, a knife edge having at least one linear or curved edge so that the nearest distance between said beam and said knife edge is 1 to 10 times the beam radius from the center of said beam, said resonator further comprising a non-linear optical crystal including a borate material, wherein said optical system generates ultraviolet rays. 
     
     
       10. An optical system having a resonator as claimed in claim  9 , wherein said optical system is a wavelength conversion optical system having at least one optical part other than mirrors in an external stable resonator, and said optical system is provided with, on at least one point in said external stable resonator, a knife edge having at least one linear or curved edge so that the nearest distance between said beam and said knife edge is 1 to 10 times the beam radius from the center of said beam. 
     
     
       11. An optical system having a stable, external resonator which is an optical system having at least one optical part other than mirrors in said stable external resonator provided with, on at least one point in said stable external resonator, an aperture having a circular hole with a diameter that is greater than 1, and less than 10, times the beam diameter at each point, said external resonator further comprising a non-linear optical crystal, wherein said optical system generates ultraviolet rays, and wherein said aperture prevents scattering induced generation of transverse mode rays generated due to scattering at said nonlinear optical crystal such that said optical system produces a stable longitudinal mode output. 
     
     
       12. An optical system having a stable, external resonator as claimed in claim  11 , wherein said optical system is a wavelength conversion optical system. 
     
     
       13. An optical system having a stable, external resonator which is an optical system having at least one optical part other than mirrors in said stable resonator provided with, on at least one point in said stable external resonator, a slit having a width that is greater than 1, and less than 10, times the beam diameter at each point, said resonator further comprising a non-linear optical crystal, wherein said optical system generates ultraviolet rays, and wherein said slit prevents scattering induced generation of transverse mode rays generated due to scattering at said nonlinear optical crystal such that said optical system produces a stable longitudinal mode output. 
     
     
       14. An optical system having a stable, external resonator as claimed in claim  13 , wherein said optical system is a wavelength conversion optical system. 
     
     
       15. An optical system having a resonator which is a wavelength conversion optical system having a plurality of mirrors and a nonlinear optical crystal for functioning as a wavelength conversion element in a stable, external resonator provided with, on an arbitrary space in said stable external resonator comprising said plurality of mirrors and optical crystal, an aperture having a dimension that is greater than 1, and less than 10, times the beam diameter at each point and having an edge of arbitrary shape, wherein said optical system generates ultraviolet rays, and wherein said aperture prevents scattering induced generation of transverse mode rays generated due to scattering at said nonlinear optical crystal such that said optical system produces a stable longitudinal mode output. 
     
     
       16. An optical system having a stable, external resonator having at least one optical part other than mirrors in a stable resonator provided with, on at least one point in said stable resonator, a knife edge having at least one linear or curved edge so that the nearest distance between a beam and said knife edge is greater than 1, and less than 10, times a beam radius from the center of said beam, said resonator further comprising a non-linear optical crystal, wherein said optical system generates ultraviolet rays, and wherein said knife-edge prevents scattering induced generation of transverse mode rays generated due to scattering at said nonlinear optical crystal such that said optical system produces a stable longitudinal mode output. 
     
     
       17. An optical system having a stable, external resonator as claimed in claim  16 , wherein said optical system is a wavelength conversion optical system. 
     
     
       18. A method for generating stable longitudinal mode output ultraviolet rays, comprising the steps of: 
       generating light rays having a fundamental wavelength that is greater than an ultraviolet wavelength;  
       resonating said light rays in a stable, external resonator;  
       generating a harmonic within said stable, external resonator by passing said fundamental wave through a nonlinear optical crystal; and blocking rays scattered outside of a beam dimension with an aperture having dimensions greater than 1, and less than 10, times the beam dimension at each point, thereby preventing scattering induced generation of transverse mode rays generated due to scattering at said nonlinear optical crystal such that an optical system produces a stable longitudinal mode output.